The present invention relates to an electroconductive polymer, to a solid electrolytic capacitor containing an electroconductive polymer, and to methods for producing them. More specifically, the present invention relates to a solid electrolytic capacitor having a reduced size, high capacity, low impedance, good moisture resistant loading property and excellent heat resistance, and to a production method thereof as well as to a highly electroconductive polymer having a novel fibril structure for use in the capacitor and to a production method of the highly electroconductive polymer
The solid electrolytic capacitor is a capacitor element manufactured by forming a dielectric oxide film layer on an anode substrate comprising a metal foil which has a large specific surface area and has generally been subjected to etching treatment, forming a solid semiconductor layer (hereinafter simply referred to as a solid electrolyte) as an counter electrode outside the dielectric layer, preferably further forming an electrically conductive layer such as an electroconductive paste on the outer face of the electrode, and connecting a lead wire thereto. The element as a whole is completely sealed with an epoxy resin or the like and is widely used as a capacitor part in electrical articles.
To cope with the demands for digitization of electrical appliances or higher speed processing of personal computers in recent years, the capacitor used therefor is also required to be compact, have a large capacity and give a low impedance in a high frequency region.
As the compact capacitor having a large capacity, solid electrolytic capacitors such as aluminum electrolytic capacitor and tantalum electrolytic capacitor have been used. However, the aluminum electrolytic capacitor has a problem in that since an ion conducting liquid electrolyte is used as the electrolytic solution, the impedance is high in the high frequency region and the temperature characteristics are bad. The tantalum electrolytic capacitor has a problem in that since a manganese oxide is used as the electrolyte and the manganese oxide has a relatively high resistivity, the impedance in the high frequency region is high.
As means to solve these problems, it has been proposed to use an electroconductive polymer having electrically conductive properties as the solid electrolyte. For example, use of an electroconductive organic material comprising a xcfx80-conjugated polymer such as polyaniline (see, JP-A-61-239617 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d)), a polypyrrole (see, JP-A-61-240625), a polythiophene derivative (see, JP-A-2-15611 (U.S. Pat. No. 4,901,645)), a polyisothianaphthene not containing a dopant (see, JP-A-62-118509), a doped polyisothianaphthene (see, JP-A-62-118511) or an intrinsic conducting polymer having an electroconductivity of from 10xe2x88x923 to 103 S/cm (see, JP-A-1-169914 (U.S. Pat. No. 4,803,596)) has been proposed.
That is, polymers having a conjugated double bond represented by polymers of aniline, pyrrole, thiophene or the like generally have a specific electroconductivity and therefore, various investigations and developments have heretofore been made thereon. In particular, the electric, magnetic and optical properties peculiar to the xcfx80-electron conjugated system of the electroconductive polymer have been taken notice of. These electroconductive polymers have been mainly produced by an electrolytic polymerization method and a chemical oxidative polymerization method.
However, according to the conventional production method, if the low molecular weight polymer obtained by the redox reaction performed on the electrode surface has poor adhesion to the electrode surface, the low molecular weight polymer dissolves or deposits in the electrolytic solution. Furthermore, if an article having a large area is intended to obtain, an electrode having a size in proportion thereto must be used, accordingly, a serious problem arises with respect to the production cost.
On the other hand, in the case of using the chemical oxidative polymerization method, an electroconductive polymer can be easily obtained by mixing a polymerizable monomer with an appropriate oxidizing agent, therefore, this simple polymerization method has been taken notice of in industry and studies and developments thereof have been made.
However, the chemical oxidative polymerization method has the following serious problem. Since the polymerization rate is proportional to the activity of the oxidizing agent, an oxidizing agent having high activity must be used. But if the polymerization is performed using a highly active oxidizing agent, an adverse side reaction readily takes place and only a polymer reduced in the structural order and having a low electroconductivity can be obtained. This problem is considered to occur because an electroconductive polymer having a conjugated double bond produced stays in the reaction system for a long period of time, therefore, the polymer skeleton having the conjugated double bond is partially destroyed by the effect of excess oxidizing agent in the reaction system, as a result, the electroconductivity decreases.
Furthermore, the electroconductive polymer obtained by the electrolytic polymerization or chemical oxidative polymerization is generally insoluble and infusible, therefore, there is an operational problem particularly in that its after processing is very difficult.
In order to solve these problems, various attempts have been made. For example, JP-A-7-130579 (U.S. Pat. No. 5,567,209) discloses a production method of a solid electrolytic capacitor using an oxide film formed on a valve-acting metal as the dielectric layer and an electroconductive polymer formed on the dielectric layer as the solid electrolyte comprising a step of coating a monomer compound solution on the surface of the above-described dielectric oxide layer and drying it to form a solid monomer compound, and a step of contacting the solid monomer compound with an oxidizing agent solution to form an electroconductive polymer layer, thereby producing a solid electrolytic capacitor having a high capacity occurrence ratio and good high-frequency properties.
JP-A-6-340754 discloses a technique of allowing polycyclic aromatic amine compound to adhere to or impregnate into an insulating substrate and contacting the substrate with a solution containing an oxidizing agent to thereby oxidatively polymerize the polycyclic aromatic amine compound inside or on the surface of the substrate.
JP-A-10-50558 discloses a production method of a solid electrolytic capacitor as an application of the electroconductive polymer, comprising impregnating an electroconductive polymer as the cathode electrolyte into a capacitor element comprising an anode member having thereon a chemical formed layer, wherein the capacitor element is immersed in a solution obtained by dissolving an oxidizing agent in a monomer which becomes an electroconductive polymer by the oxidative polymerization, thereby forming an electroconductive polymer layer within the capacitor element, so that a compact capacitor having a large capacity can be produced.
JP-A-10-50559 discloses a technique, which is an application of the electroconductive polymer to a solid electrolytic capacitor comprising a step of immersing a capacitor element in an oxidizing agent solution and then evaporating the solvent component, thereby precipitating an oxidizing agent within the capacitor element, and a step of immersing the capacitor element in a solution containing a monomer which becomes an electroconductive polymer by the oxidative polymerization, thereby allowing the oxidizing agent to act on the monomer, so that high-temperature load properties can be improved.
Furthermore, JP-A-9-289141 (EP-A-803885) proposes a production method of a solid electrolytic capacitor, comprising immersing a porous electrode material in a monomer salt solution kept at a temperature higher than the dissolution temperature, cooling the porous material to precipitate the monomer salt on the surface thereof, and immersing the porous material in a solution containing an oxidizing agent.
As a solid electrolyte formed on the dielectric film layer, an electroconductive metal oxide and an electroconductive polymer have been had attention because they are expected to be basically possible for attaining a sufficiently high electroconductivity. However, they have a problem in that if the electroconductivity exceeds the proper range, the leakage current greatly increases to cause short circuit, whereas if the electroconductivity is low, the frequency properties are deteriorated and the capacity greatly decreases. As such, the control of the electroconductivity to fall within a proper range and the thermal stability of the solid electrolyte are still in need of improvement.
Conventional capacitors using an electroconductive polymer such as polypyrrole have a problem that the capacitor properties greatly fluctuate depending on the moisture resistance under load. In connection therewith, heat resistance is keenly demanded. For example, the resistance to heat by reflow soldering property at the formation from a capacitor element into a capacitor part is important and a capacitor element having high heat resistance is demanded. In other words, conventional techniques have a problem in the solid electrolyte produced on the oxide film layer and the production method thereof.
Specifically, the technique disclosed in JP-A-7-130579 (U.S. Pat. No. 5,567,209), in which the monomer compound solution is dried to form a solid-like monomer, has a problem in that the polymerization rate may decrease as the polymerization degree of the polymer composition increases since the diffusion of monomers are restricted in the solid monomer phase.
The technique disclosed in JP-A-6-340754 relates to a method for forming a transparent electroconductive thin film on an insulting material, and does not refer to the shape or performance of the polymer which has a fibril structure obtained by the polymerization positively effected at the interface.
The technique disclosed in JP-A-10-50558 is a technique of forming an electroconductive polymer thin film on a chemical formed film layer but an oxidizing agent is dissolved directly in the monomer which becomes an electroconductive polymer by the oxidative polymerization, therefore, the oxidative polymerization also proceeds in the monomer solution to form a polymer before and while it is used and it is difficult to maintain a uniform monomer solution all the time. Thus, this is an unstable production method failing in bringing out stable performance.
According to the technique disclosed in JP-A-10-50559, an oxidizing agent solution is introduced into pores, the solvent is evaporated to precipitate crystals of the oxidizing agent, and then the oxidative polymerization is performed. In view of the process, however, this is an inefficient production method in industry because a step of precipitating the oxidizing agent into pores on the chemical formed surface of a metal foil is indispensable and as duly understood, the area where the solid oxidizing agent contacts with the monomer is very small, therefore, the polymerization reaction proceeds slowly.
Furthermore, the technique disclosed in JP-A-9-289141 (EP-A-803885), in which the polymerizable monomer is solid has the same problem as in the technique disclosed in JP-A-10-50559.
An object of the present invention is to provide a highly electroconductive polymer having a conjugated double bond (xcfx80 electron conjugated system) used advantageously as a solid electrolyte for a solid electrolytic capacitor.
Another object of the present invention is to provide a method for producing the above novel polymer having a conjugated double bond by way of oxidative polymerization, which polymer has an higher electroconductivity than other polymers having the same chemical composition.
Still another object of the present invention is to provide a solid electrolytic capacitor comprising the above highly electroconductive polymer as a solid electrolyte and having not only good initial properties but also excellent long-term reliability such as durability at high temperature and high humidity and a method for producing the same.
As a result of extensive investigations under these circumstances, it has been first found that slowly contacting a solution having dissolved therein a polymerizable monomer alone or together with an electrolyte having a doping action with a solution of an oxidizing agent having a polymerization initiating ability on an interface to polymerize the monomer can give rise to a highly electroconductive polymer having a scaly fibrillar structure and that practicing this polymerization method on a dielectric film layer and utilizing the resulting film composition having a fibril structure as a solid electrolyte can provide a capacitor excellent in initial properties (loss factor, leakage current, heat resistance, equivalent series resistance in high frequency regions, low impedance, etc.) and long term reliability (durability at high temperature and high humidity, etc.). The present invention has been accomplished based on this finding.
Therefore, the present invention provides the following solid electrolytic capacitor, its production method, electroconductive polymer and its production method:
[1] A solid electrolytic capacitor comprising a dielectric film layer on a porous valve-acting metal and a solid electrolytic layer comprised by a polymer having a fibril structure formed on said dielectric film layer.
[2] The solid electrolytic capacitor as described in [1] above, wherein the solid polymer electrolytic layer is an electroconductive polymer having a fibril structure comprising as a repeating unit a structure having a thiophene-diyl skeleton represented by the following general formula (1): 
(wherein R1 and R2 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R1 and R2 may combine with each other at any position to form a divalent chain for forming a 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R1 and R2, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, xcex4 represents a number in the range of from 0 to 1, Z represents an anion, and j represents a valence of Z and is 1 or 2).
[3] The solid electrolytic capacitor as described in [1] above, wherein the solid polymer electrolytic layer is an electroconductive polymer having a fibril structure comprising as a repeating unit a structure having a condensed polycyclic skeleton represented by the following general formula (2): 
(wherein R3, R4, R5, R6, R7 and R8 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R3, R4, R5, R6, R7 or R8 may combine with each other at any position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R3, R4, R5, R6, R7 or R8, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, k represents the number of condensed rings surrounded by the thiophene ring and the benzene ring having the substituents R3 to R6 and is 0 or an integer of from 1 to 3, the condensed ring in the formula may contain an optional number of nitrogen or N-oxide, with the proviso that the substituents R3 to R8 are deducted by the number of nitrogen or N-oxide, xcex4 represents a number in the range of from 0 to 1, Z represents an anion, and j represents a valence of Z and is 1 or 2).
[4] The solid electrolytic capacitor as described in [1] above, wherein said solid polymer electrolytic layer is an electroconductive polymer having a fibril structure comprising as a repeating unit a structure having a pyrrole-diyl skeleton represented by the following general formula (3): 
(wherein R9 and R10 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R9 and R10 may combine with each other at an optional position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R9 and R10, and the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, xcex4 represents a number in the range of from 0 to 1, Z represents an anion, and ; represents a valence of Z and is 1 or 2).
[5] The solid electrolytic capacitor as described in [1] above, wherein the solid polymer electrolytic layer is an electroconductive polymer having a fibril structure comprising as a repeating unit a structure having a furan-diyl skeleton represented by the following general formula (4): 
(wherein the substituents R11 and R12 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R11 and R12 may combine with each other at any position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R11 and R12, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, xcex4 represents a number in the range of from 0 to 1, Z represents an anion, and j represents a valence of Z and is 1 or 2).
[6] The solid electrolytic capacitor as described in [1] above, wherein the solid polymer electrolytic layer is an electroconductive polymer having a fibril structure comprising as a repeating unit a structure having an iminophenylene skeleton represented by the following general formula (5): 
(wherein the substituents R13, R14, R15 and R16 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R13, R14, R15 or R16 may combine with each other at any position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R13, R14, R15 or R6, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and amino at any position, xcex4 represents a number in the range of from 0 to 1, Z represents an anion, and j represents a valence of Z and is 1 or 2).
[7] The solid electrolytic capacitor as described in [2] above, wherein said solid polymer electrolyte has an electroconductivity of from about 0.1 to about 200 S/cm.
[8] A method for producing a solid electrolytic capacitor comprising a solid electrolytic layer composed of a polymer having a fibril structure on a dielectric film layer of a porous valve-acting metal, which comprises the step of contacting a polymerizable monomer with a single solution containing an oxidizing agent having a polymerization initiating ability kept in the saturated or supersaturated state or a mixed solution containing the oxidizing agent and an electrolyte having a doping action on said dielectric film, thereby forming a composition in the form of a film of a polymer having a fibril structure on said dielectric film.
[9] A method for producing a solid electrolytic capacitor, comprising a solid electrolytic layer composed of a polymer having a fibril structure on a dielectric film layer of a porous valve-acting metal, which comprises the step of contacting a solution having dissolved therein a polymerizable monomer alone or together with an electrolyte having a doping action with a single solution containing an oxidizing agent having a polymerization initiating ability kept in the saturated or supersaturated state or a mixed solution containing the oxidizing agent and an electrolyte having a doping action on said dielectric film, thereby forming a composition in the form of a film of a polymer having a fibril structure on said dielectric film.
[10] The method for producing a solid electrolytic capacitor as described in [8] above, which comprises the step of contacting on said dielectric film a polymerizable monomer represented by the following general formula (6): 
(wherein R1 and R2 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a trihalomethyl group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R1 and R2 may combine with each other at any position to form a divalent chain for forming a 3 -, 4 -, 5 -, 6 - or 7 -membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R1 and R2, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position) with a solution containing an oxidizing agent having a polymerization initiating ability, thereby forming a composition in the form of a film of a polymer having a fibril structure on said dielectric film.
[11] The method for producing a solid electrolytic capacitor as described in [8] above, which comprises the step of contacting on said dielectric film a polymerizable monomer represented by the following general formula (7): 
(wherein the substituents R3, R4, R5, R6, R7 and R8 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R3, R4, R5, R6, R7 or R8 may combine with each other at any position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R3, R4, R5, R6, R7 or R8, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, k represents the number of condensed rings surrounded by the thiophene ring and the benzene ring having the substituents R3 to R6 and is 0 or an integer of from 1 to 3, the condensed ring in the formula may contain an optional number of nitrogen or N-oxide, with the proviso that the substituents R3 to R8 are deducted by the number of nitrogen or N-oxide) with a solution containing an oxidizing agent having a polymerization initiating ability, thereby forming a composition in the form of a film of a polymer having a fibril structure on said dielectric film.
[12] The method for producing a solid electrolytic capacitor as described in [8] above, which comprises the step of contacting on said dielectric film a polymerizable monomer represented by the following general formula (8): 
(wherein the substituents R9 and R10 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R9 and R10 may combine with each other at an optional position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R9 and R10, and the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and amino at any position) with a solution containing an oxidizing agent having a polymerization initiating ability, thereby forming a composition in the form of a film of a polymer having a fibril structure on said dielectric film.
[13] The method for producing a solid electrolytic capacitor as described in [8] above, which comprises the step of contacting on said dielectric film a polymerizable monomer represented by the following general formula (9): 
(wherein the substituents R11 and R12 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R11 and R12 may combine with each other at any position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R11 and R12, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position) with a solution containing an oxidizing agent having a polymerization initiating ability, thereby forming a composition in the form of a film of a polymer having a fibril structure on said dielectric film.
[14] The method for producing a solid electrolytic capacitor as described in [8] above, which comprises the step of contacting on said dielectric film a polymerizable monomer represented by the following general formula (10): 
(wherein the substituents R13, R14, R15 and R16each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R13, R14, R15 or R16 may combine with each other at any position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R13, R14, R15 or R16, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position) with a solution containing an oxidizing agent having a polymerization initiating ability, thereby forming a composition in the form of a film of a polymer having a fibril structure on said dielectric film.
[15] The method for producing a solid electrolytic capacitor as described in [9] above, wherein the polymerizable monomer has a concentration of from 0.01 to 5 mol/L.
[16] The method for producing a solid electrolytic capacitor as described in [8] above, wherein the electrolyte having a doping action has a concentration of from 0.001 to 2.5 mol/L.
[17] The method for producing a solid electrolytic capacitor as described in [8] above, wherein the oxidizing agent having a polymerization initiating ability is at least one compound selected from persulfates, bichromates and trivalent iron salts.
[18] The method for producing a solid electrolytic capacitor as described in [8] above, wherein the concentration of the oxidizing agent having a polymerization initiating ability is from 0.01 to 5 times the concentration of the polymerizable monomer.
[19] The method for producing a solid electrolytic capacitor as described in [8] above, wherein the step of forming a solid polymer electrolyte is repeated from 2 to 30 times to form compositions each of which is in the form of a film.
[20] A highly electroconductive polymer having a fibril structure comprising as a repeating unit a structure having a thiophene-diyl skeleton represented by the following general formula (1): 
(wherein the substituents R1 and R2 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group. The hydrocarbon chains of R1 and R2 may combine with each other at any position to form a divalent chain for forming a 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R1 and R2, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, xcex4 represents a number in the range of from 0 to 1, Z represents an anion, and j represents a valence of Z and is 1 or 2).
[21] A highly electroconductive polymer having a fibril structure comprising as a repeating unit a structure having a condensed polycyclic skeleton represented by the following general formula (2): 
(wherein the substituents of R3, R4, R5, R6, R7 and R8 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy and alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group. The hydrocarbon chains of R3, R4, R5, R6, R7 or R8 may combine with each other at any position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R3, R4, R5, R6, R7 or R8, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, k represents the number of condensed rings surrounded by the thiophene ring and the benzene ring having the substituents R3 to R6 and is 0 or an integer of from 1 to 3, the condensed ring in the formula may optionally contain nitrogen or N-oxide, with the proviso that the substituents R3 to R8 are deducted by the number of nitrogen or N-oxide, xcex4 represents a number in the range of from 0 to 1, Z represents an anion, and j represents a valence of Z and is 1 or 2).
[22] A highly electroconductive polymer having a fibril structure comprising as a repeating unit a structure having a pyrrole-diyl skeleton represented by the following general formula (3): 
(wherein R9 and R10 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R9 and R10 may combine with each other at an optional position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R9 and R10, and the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, xcex4 represents a number in the range of from 0 to 1, Z represents an anion, and j represents a valence of Z and is 1 or 2).
[23] A highly electroconductive polymer having a fibril structure comprising as a repeating unit a structure having a furan-diyl skeleton represented by the following general formula (4): 
(wherein the substituents R11 and R12 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R11 and R12 may combine with each other at any position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R11 and R12, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, xcex4 represents a number in the range of from 0 to 1, Z represents an anion, and j represents a valence of Z and is 1 or 2).
[24] A highly electroconductive polymer having a fibril structure comprising as a repeating unit a structure having an iminophenylene skeleton represented by the following general formula (5): 
(wherein the substituents R13, R14, R15 and R16 each independently represent a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkyl ester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF3 group, a phenyl group and a substituted phenyl group, the hydrocarbon chains of R13, R14, R15 or R16 may combine with each other at any position to form a divalent chain for forming at least one 3-, 4-, 5-, 6- or 7-membered saturated or unsaturated hydrocarbon cyclic structure together with the carbon atoms substituted by R13, R14, R15 or R16, the cyclic bonded chain may optionally contain a bond such as carbonyl, ether, ester, amide, sulfide, sulfinyl, sulfonyl and imino at any position, xcex4 represents a number in the range of from 0 to 1, Z represents an anion, and j represents a valence of Z and is 1 or 2).
[25] A method for producing a highly electroconductive polymer having a fibril structure, comprising contacting at least one polymerizable monomer represented by the following general formula (6): 
(wherein R1 and R2 have the same meanings as in [10] above); the general formula (7): 
(wherein R3, R4, R5, R6, R7 and R8 have the same meanings as in [11] above); the general formula (8): 
(wherein R9 and R10 have the same meanings as in [12] above); the general formula (9): 
(wherein R11 and R12 have the same meanings as in [13] above); or the general formula (10): 
(wherein R13, R14, R15 and R16 have the same meanings as in [14] above) with a solution containing an oxidizing agent having a polymerization initiating ability such that an interface is formed therebetween, and performing polymerization at said interface.
[26] The method for producing a highly electroconductive polymer having a fibril structure as described in [25] above, comprising contacting a solution obtained by dissolving at least one polymerizable monomer represented by formula (6), (7), (8), (9) or (10) as described in [25] above in a solvent with a solution containing an oxidizing agent having a polymerization initiating ability such that an interface is formed therebetween, and performing polymerization at said interface.
[27] The method for producing a highly electroconductive polymer having a fibril structure as described in [25] above, wherein the solution containing an oxidizing agent having a polymerization initiating ability contains an electrolyte having a doping action.
[28] The method for producing a highly electroconductive polymer having a fibril structure as described in [25] above, wherein the solution containing an oxidizing agent having a polymerization initiating ability is a saturated or supersaturated solution.
[29] The method for producing a highly electroconductive polymer having a fibril structure as described in [25] above, wherein a saturated solution of an oxidizing agent having a polymerization initiating ability is produced, the oxidizing agent solution is contacted with the polymerizable monomer at a temperature lower than the temperature at the production of said saturated solution to form a interface, and then polymerization is performed.
[30] The method for producing a highly electroconductive polymer having a fibril structure as described in [25] above, wherein the oxidizing agent having a polymerization initiating agent is at least one of a persulfate, a bichromate and a trivalent iron salt.
[31] The method for producing a highly electroconductive polymer having a fibril structure as described in [26] above, wherein the solvent is a hydrophilic organic solvent capable of dissolving the polymerizable monomer.
[32] The method for producing a highly electroconductive polymer having a fibril structure as described in [25] above, wherein the polymerizable monomer is contacted with the solution containing an oxidizing agent to produce a highly electroconductive polymer having a fibril structure and after washing or not washing the polymer, the method for producing a highly electroconductive polymer having a fibril structure described in [25] above is performed two or more times on the surface of the highly electroconductive polymer having a fibril structure to stack polymer composition layers.
[33] The method for producing a highly electroconductive polymer having a fibril structure as described in [26] above, wherein the polymerizable monomer is contacted with the solution containing an oxidizing agent to produce a highly electroconductive polymer having a fibril structure and after washing or not washing the polymer, the method for producing a highly electroconductive polymer having a fibril structure described in [26] above is performed two or more times on the surface of the highly electroconductive polymer having a fibril structure to stack polymer composition layers.